Linear compressor

ABSTRACT

Disclosed herein is a linear compressor having a stator cover, which is designed in such a fashion that a section of the stator cover not to be fastened with bolts has a curvature smaller than the remaining section thereof to be fastened with the bolt so as to be reduced in size thereof. This enables the stator cover to be spaced apart from the shell by a sufficient distance, thereby achieving a size reduction of the shell and a small-scale linear compressor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a linear compressor, and more particularly, to a linear compressor having a stator cover, which is fabricated through sheet metal forming to have two or more curvatures so as to be spaced apart from a shell by a sufficient distance, thereby enabling a size reduction of the shell and achieving a small-scale linear compressor.

2. Description of the Related Art

Generally, linear compressors are machines used to suction and compress fluid, such as refrigerant gas, and discharge the compressed fluid as a piston is rectilinearly reciprocated in a cylinder by making use of driving power of a linear motor.

FIGS. 1 and 2 are a front sectional view and a side sectional view, respectively, illustrating a linear compressor according to the prior art.

As shown in FIGS. 1 and 2, the linear compressor of the prior art comprises: a shell 2 in which oil O is received; and a liner compressing unit 10 installed to vibrate under operation of dampers mounted in the shell 2 and adapted to suction and compress fluid, and discharge the compressed fluid.

A fluid suction pipe 4 and a fluid discharge pipe 5 pass into the shell 2, and the fluid discharge pipe 5 is also connected to the linear compressing unit 10.

The linear compressing unit 10 comprises: a cylinder frame 12 in which a cylinder 11 is mounted; a back cover 14 having a fluid suction channel 13; a piston 16 rectilinearly reciprocably disposed in the cylinder 11 and internally defining a fluid suction channel 15 for allowing the fluid to be suctioned into the cylinder 11; a linear motor 20 for rectilinearly reciprocating the piston 16; and a discharge valve assembly 17 provided to open or close a front end of the cylinder 11 and connected to the fluid discharge pipe 5.

The linear motor 20 is a combination of stator means and mover means. The stator means includes an outer stator 21, an inner stator 22, a bobbin 23 mounted in the outer stator 21, and a coil 24 wound on the bobbin 23 to create an electromagnetic field. The mover means includes a magnet 25 adapted to rectilinearly move upon receiving a magnetic force produced by the coil 24, and a magnet frame 26 for fixing the magnet 25.

The cylinder frame 12 is located in front of the linear motor 20, and in rear of the linear motor 20 is located a stator cover 27. The outer stator 21 is fixed to the stator cover 27. The cylinder frame 12 and the stator cover 27 are axially fastened to the outer stator 21 by means of bolts 30 and nuts 31 to exert an axial compression force to the outer stator 21.

The cylinder frame 12 is formed with first through-holes 28 circumferentially spaced apart from one another by a predetermined angle so that the bolts 30 penetrate therethrough, respectively. The stator cover 27 is formed with second through-holes 29 positioned to correspond to the first through-holes 28 so that the bolts 30 penetrate therethrough, respectively.

Below the linear compressing unit 10 is mounted an oil supply unit 33. The oil supply unit 33 serves to supply the oil O, received in the shell 2, into the linear compressing unit 10 upon vibration of the linear compressing unit 10 for the lubrication/cooling of the cylinder 11 and the piston 16.

The oil supply unit 30 comprises: an oil cylinder 34 fixedly mounted below the linear motor 20; an oil piston 35 rectilinearly reciprocably disposed in the oil cylinder 34; and first and second oil springs 36 and 37 disposed in the oil cylinder 34 to elastically support the oil piston 35.

The linear compressing unit 10 has an oil suction channel 38 connected to the oil cylinder 34 for the passage of the oil O, and an oil discharge channel 39.

One end of the oil cylinder 34 is formed with an oil inlet 40 for allowing the oil O received in the shell 2 to be introduced into the oil cylinder 34, whereas the other end of the oil cylinder 34 is formed with an oil outlet 41 communicating with the oil suction channel 38.

An oil suction cover 42 is mounted between the oil cylinder 34 and the stator cover 27 so as to partially shield the oil inlet 40 and to support an outer end of the second oil spring 37. An oil discharge cover 43 is mounted to the cylinder frame 12 to define an oil passage 44 therebetween.

The oil piston 35, inserted in the oil cylinder 34, internally defines an oil channel 45.

To an exit of the oil channel 45 defined in the oil piston 35 is mounted an oil suction valve 46, which is supported by the first oil spring 36, and to the oil outlet 41 of the oil cylinder 34 is mounted an oil discharge valve 47.

Now, the operation of the linear compressor according to the prior art configured as stated above will be explained.

When driving power is applied to the coil 24 of the outer stator 21, the coil 24 creates an electromagnetic field between the outer stator 21 and the inner stator 22, thereby serving to rectilinearly reciprocate the magnet 25. Upon rectilinear reciprocation of the magnet 25, both the magnet frame 26 and the piston 16 are rectilinearly reciprocated, allowing the fluid, which is suctioned into a compression chamber C defined in the cylinder 11 by passing through the fluid suction pipe 4 and the fluid suction channel 13, to be compressed and discharged to the outside via the fluid discharge pipe 5.

As the fluid is repeatedly compressed in and discharged from the compression chamber C, the oil O received in a bottom region of the shell 2 is suctioned into the oil cylinder 34 on the basis of pressure variation in the oil cylinder 34, and then is discharged to the outside of the linear compressing unit 10 after being used to lubricate/cool the cylinder 11 and the piston 16.

That is, when the linear compressing unit 10 vibrates, the vibration of the linear compressing unit 10 is transmitted to the oil cylinder 34, causing the oil piston 35 to slide in the oil cylinder 34 by virtue of its own inertia against movement of the oil cylinder 34, so as to suction the oil O and discharge it.

When the oil piston 35 moves backward, a low pressure is produced in front of the oil piston 35 and the oil suction valve 46 is opened, so that the oil O in the shell 2 is introduced via the oil inlet 40 to pass through the oil passage 45 defined in the oil piston 35.

In succession, when the oil piston 35 moves forward, a high pressure is produced in front of the oil piston 35 to open the oil discharge valve 47, so that the oil O is supplied into a gap between the cylinder 11 and the piston 16 by passing through the oil passage 44 defined in the oil discharge cover 43 and the oil suction channel 38.

Meanwhile, in order to mount the outer stator 21 of the linear motor 20, the outer stator 21 is first interposed between the cylinder frame 12 and the stator cover 27, and then the bolts 30 and the nuts 31 are fastened and tightened so that the outer stator 21 is pressed against the cylinder frame 12 and the stator cover 27. In this way, the outer stator 21 is fixedly mounted.

Here, a plurality of the bolts 30 and the nuts 31 are radially spaced apart from one another by a predetermined angle.

In the above described linear compressor of the prior art, however, due to the fact that the stator cover 27 is fastened relative to the cylinder frame 12 by means of the plurality of bolts 30 and nuts 31 while being spaced apart from the shell 2 by a predetermined distance, the stator cover 27 must have a circular form and a plurality of fastening through-holes for the bolts 30. This has a problem in that it is difficult to reduce the size of the stator cover 27 and to achieve a small-scale linear compressor.

In addition, the stator cover 27 of the prior art has no function of supporting the oil cylinder 34 and thus requires the oil suction cover 42 that is capable of supporting the oil cylinder 34 against the stator cover 27 and supporting the end of the second oil spring 37, resulting in an increase in the number of elements constituting the compressor.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a linear compressor having a stator cover, which is fabricated through sheet metal forming to have two or more curvatures, thereby enabling a size reduction of the shell and achieving a small-scale linear compressor.

It is another object of the present invention to provide a linear compressor which is designed in such a fashion that an oil cylinder is supported by a stator cover, thereby being capable of achieving a reduction in the number of elements, and a simplified structure of the linear compressor.

In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a linear compressor comprising: a shell; a linear motor mounted in the shell; a cylinder frame mounted in front of the linear motor; a stator cover mounted in rear of the linear motor; a piston rectilinearly reciprocably disposed in a cylinder mounted in the cylinder frame; and fastening device for fixing the cylinder frame and the stator cover relative to each other, wherein the stator cover is formed to have two or more curvatures.

Preferably, the stator cover may have a plurality of through-holes for the penetration of the fastening device.

Preferably, the stator cover may be configured so that a curvature of a section of the stator cover not formed with the through-holes is smaller than a curvature of the remaining section of the stator cover formed with the through-holes.

Preferably, the fastening device may include: bolts for axially penetrating through the cylinder frame and the stator cover; and nuts to be fastened to the bolts, respectively.

In accordance with another aspect of the present invention, the above and other objects can be accomplished by the provision of a linear compressor comprising: a shell in which oil is received; a linear motor mounted in the shell; a cylinder frame mounted in front of the linear motor; a stator cover mounted in rear of the linear motor; a piston rectilinearly reciprocably disposed in a cylinder mounted in the cylinder frame; fastening device for fixing the cylinder frame and the stator cover relative to each other; and oil supply device supported at opposite ends thereof against the cylinder frame and the stator cover and adapted to supply the oil received in the shell into a gap between the piston and the cylinder, wherein the stator cover is configured so that a lower section of the stator cover supporting the oil supply device has a curvature smaller than a curvature of an upper section of the stator cover.

Preferably, the oil supply device may include: an oil pump mounted between the cylinder frame and the stator cover to pump the oil received in the shell; an oil suction channel for introducing the oil from the oil pump into the gap between the cylinder and the piston; and an oil discharge channel for discharging the oil between the cylinder and the piston to the outside of the cylinder.

Preferably, the oil pump has: oil cylinder having an oil inlet and an oil outlet formed at opposite ends thereof; an oil piston rectilinearly reciprocably disposed in the oil cylinder; and first and second oil springs disposed in the oil cylinder to elastically support opposite ends of the oil piston.

Preferably, the stator cover may have an oil inlet formed at a lower region thereof to correspond to the oil inlet of the oil cylinder.

Preferably, the stator cover may have a plurality of through-holes radially spaced apart from one another by a predetermined angle for the fitting of the fastening device.

Preferably, the stator cover may be configured so that a section of the stator cover not formed with the through-holes has a curvature smaller than that of the section of the stator cover formed with the through-holes.

In the linear compressor according to the present invention, the stator cover is configured in such a fashion t h a t the section not formed with the bolt fastening through-holes has the curvature smaller than that of the section formed with the through-holes so as to enable a size reduction of the stator cover while defining a sufficient space between the stator cover and the shell, thereby enabling reduction of the size of the shell, achieving a small-scale linear compressor.

Further, according to the present invention, a curvature in a lower region of the stator cover is larger than that of an upper region of the stator cover in order to sufficiently support an end of the oil cylinder without requiring a separate supporting element, such as an oil suction cover. Thereby, the number of elements constituting the linear compressor is reduced, resulting in a reduction of the manufacturing cost. By omitting the oil suction cover, further, it is possible to prevent a deterioration of oil supply efficiency caused when the oil suction cover is misassembled, thereby being capable of improving operational reliability and reducing noise produced due to shaking of the oil suction cover.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a front sectional view illustrating the interior structure of a linear compressor according to the prior art;

FIG. 2 is a schematic side sectional view of the linear compressor shown in FIG. 1, illustrating how a stator cover of the linear compressor is mounted;

FIG. 3 is a front sectional view illustrating the interior structure of a linear compressor in accordance with a first embodiment of the present invention;

FIG. 4 is an exploded perspective view illustrating how a linear motor of the linear compressor shown in FIG. 3 is assembled;

FIG. 5 is a schematic side sectional view of the linear compressor shown in FIG. 3, illustrating how a stator cover of the linear compressor is mounted;

FIG. 6 is a front sectional view illustrating a linear compressor in accordance with a second embodiment of the present invention; and

FIG. 7 is a schematic side sectional view of the linear compressor shown in FIG. 6, illustrating how a stator cover of the linear compressor is mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of a linear compressor according to the present invention will be explained with reference to the accompanying drawings.

FIG. 3 is a front sectional view illustrating a linear compressor in accordance with a first embodiment of the present invention.

As shown in FIG. 3, the linear compressor of the present invention comprises a linear compressing unit 60 mounted in a shell 50 in a shock-absorbing manner. The shell 50 is divided into a lower shell 51 having an open upper surface and an upper shell 52 configured to cover the upper surface of the lower shell 51. The lower and upper shells 51 and 52 are coupled to each other to define a hermetically sealed interior space therebetween. In a bottom region of the lower shell 51 is received oil O.

A fluid suction pipe 53 and a fluid discharge pipe 54 pass into the shell 50. The fluid discharge pipe 54 is also connected to the linear compressing unit 60 to discharge fluid, compressed in the linear compressing unit 60, to the outside. The linear compressing unit 60 is supported on dampers 55 mounted in the lower shell 51 so as to vibrate by means of the dampers 55.

The linear compressing unit 60 comprises: a liner motor 61 for generating driving power; a cylinder frame 63 coupled to a front end of the linear motor 61 and internally mounted with a cylinder 62; a stator cover 64 coupled to a rear end of the linear motor 61; a back cover 66 having a fluid suction channel 65; a piston 69 rectilinearly reciprocably disposed in the cylinder 62 and internally defining a fluid suction channel 67 and a fluid suction port 68 for allowing the fluid to be suctioned into the cylinder 62; a discharge valve assembly 70 located in front of the cylinder 62 to define a compression chamber C between a front end of the cylinder 62 and the piston 69 and adapted to discharge the fluid compressed in the compression chamber C to the fluid discharge pipe 54, and oil supply device for supplying the oil O received in the bottom region of the shell 50 into a gap between the cylinder 62 and the piston 69.

A muffler 84 is interposed between a rear end of the piston 69 and the fluid suction channel 65 of the back cover 66 for reducing operational noise.

Here, at the rear end of the piston 69 is formed a flange 71 so that the flange 71 is coupled to the linear motor 61 by means of fastening bolts to transmit the driving power of the linear motor 61 to the piston 69. To a front end of the piston 69 is mounted a suction valve 72 for opening or closing the suction port 68.

The linear motor 61 comprises: a plurality of outer stators 78 located between the cylinder frame 63 and the stator cover 64; a bobbin 79 provided inside the outer stators 78; a coil 80 wound on the bobbin 79; an inner stator 81 mounted on the cylinder frame 63 so that a predetermined gap is defined between the outer stators 78 and the inner stator 81; a magnet 82 disposed between the outer stators 78 and the inner stator 81 to rectilinearly reciprocate by making use of electromagnetic force produced by the coil 80; and a magnet frame 83 coupled to the flange 71 of the piston 69 so as to fix the magnet 82 so that rectilinear movement force of the magnet 82 is transmitted to the piston 69.

The bobbin 79 has a cylindrical form, and the plurality of outer stators 78 are radially arranged on the bobbin 79 so that they are spaced apart from one another by a predetermined angle.

The discharge valve assembly 70 comprises: a discharge valve 73 for opening or closing the compression chamber C defined in the cylinder 62; an inner discharge cover 75 configured to elastically support the discharge valve 73 by means of a discharge spring 74 and formed with fluid discharge holes; an outer discharge cover 76 coupled external to the inner discharge cover 75 to define a predetermined space therebetween; and a connection pipe 77 mounted to the outer discharge cover 76 to be connected to the fluid discharge pipe 54.

The oil supply device comprises: an oil pump 90 mounted between the cylinder frame 63 and the stator cover 64 to pump the oil O received in the shell 50; an oil suction channel 97 for introducing the oil O from the oil pump 90 into the gap between the cylinder 62 and the piston 69; and an oil discharge channel 98 for discharging the oil O between the cylinder 62 and the piston 69 to the outside of the cylinder 62.

The oil pump 90 has: an oil cylinder 93 having an oil inlet 91 and an oil outlet 92 formed at opposite ends thereof; an oil piston 94 rectilinearly reciprocably disposed in the oil cylinder 93; and first and second oil springs 95 and 96 disposed in the oil cylinder 93 to elastically support opposite ends of the oil piston 94.

The oil suction channel 97 is a combination of an oil passage 100, a cylinder frame suction channel 101, and a cylinder suction channel 102. The oil passage 100 is defined between the cylinder frame 63 and an oil discharge cover 99 mounted to the cylinder frame 63. The cylinder frame suction channel 101 is defined in the cylinder frame 63 to allow the oil suctioned through the oil passage 100 to pass through the cylinder frame 63. The cylinder suction channel 102 is defined to supply the oil suctioned through the cylinder frame suction channel 101 into the gap between the cylinder 62 and the piston 69.

To the oil inlet 91 is mounted an oil suction cover 103 in order to support an end of the second oil spring 96 and to allow the oil cylinder 93 to support the stator cover 64 at an end thereof.

Throughout the interior of the oil piston 94 is longitudinally defined an oil channel 104 for allowing the oil introduced from the oil inlet 91 to pass through the oil piston 94. To an exit of the oil channel 104 is mounted an oil suction valve 105, and between the oil cylinder 93 and the oil discharge cover 99 is mounted an oil discharge valve 106.

FIG. 4 is an exploded perspective view illustrating how the linear motor 61 of the linear compressor shown in FIG. 3 is assembled, and FIG. 5 is a schematic side sectional view illustrating how the stator cover 64 of the linear compressor is mounted.

As shown in FIGS. 4 and 5, the stator cover 64 and the cylinder frame 63 are axially fastened to the outer stators 78 by means of fastening device so as to exert a compression force to the outer stators 78. The fastening device include: bolts 107 having a predetermined sufficient length to axially penetrate through the cylinder frame 63 and the stator cover 64; and nuts 108 fastened to the bolts 107, respectively.

Here, the stator cover 64 has: a disk portion 109 configured to come into close contact with the outer stators 78 and having a center opening, and a flange portion 110 protruding rearward from the circumference of the disk portion 109.

The cylinder frame 63 is circumferentially formed with a plurality of through-holes 111 for the penetration of the bolts 107, and correspondingly, the disk portion 109 of the stator cover 64 is circumferentially formed with a plurality of through-holes 112 for the bolts 107. The bolts 117, fastened through the through-holes 111 and 112, are finally fastened with the nuts 108.

The plurality of through-holes 112, formed at the disk portion 109 of the stator cover 64, are radially spaced apart from one another by a predetermined angle so that they correspond to the through-holes 111 of the cylinder frame 63 in a one to one ratio.

In the present embodiment, the disposition of the through-holes 111 and 112 is defined and explained that four through-holes 111 and four through-holes 112 formed at the cylinder frame 63 and the stator cover 64 are spaced apart from one another by an angle of 90°.

Meanwhile, the stator cover 64 has a non-circular form having two or more curvatures so that an outer circumference of the stator cover 64 is spaced apart from the shell 50 to define a predetermined space required for the fastening of the bolts 107.

That is, the present embodiment will be defined and explained in such a fashion that a section of the stator cover 64 not formed with the through-holes 112 has a curvature K 2 smaller than a curvature K 1 of the remaining section of the stator cover 64 formed with the through-holes 112.

Here, the curvatures K 1 and K 2 are reciprocal values of radii of curvature ρ1 and ρ2. The smaller the curvatures K 1 and K 2 are, the larger the radii of curvature ρ1 and ρ2, resulting in a smooth contour of the stator cover 64.

As can be seen from FIG. 5, the stator cover 64 must be reduced in size in the section thereof not formed with the through-holes 112 so that it is sufficiently spaced apart from the shell 50. Therefore, the radius of curvature ρ2 of the section not formed with the through-holes 112 is preferably larger than the radius of curvature ρ1 of the remaining section of the stator cover 64 formed with the through-holes 112.

On the other hand, the section of the stator cover 64 formed with the through-holes 112 has the radius of curvature ρ1 smaller than the radius of curvature ρ2 of the remaining section of the stator cover 64 not formed with the through-holes 112, in order to ensure a sufficient fastening space for the bolts 107 while reinforcing the structural strength of the stator cover 64.

Here, the stator cover 64 is fabricated through sheet metal forming so that the stator cover 64 is easy to design and manufacture.

Now, the operation of the linear compressor configured as stated above according to the first embodiment of the present invention will be explained.

First, when a driving voltage is applied to the coil 87, a magnetic field is produced around the coil 80, causing the magnet 82 to rectilinearly reciprocate through interaction with the magnetic field. Such rectilinear reciprocation of the magnet 82 is transmitted to the piston 69 via the magnet frame 83, resulting in rectilinear reciprocation of the piston 69 in the cylinder 62.

As the piston 69 rectilinearly reciprocates, the suction valve 72 and the discharge valve 73 are opened or closed on the basis of pressure difference between front and rear sides of the compression chamber C. Thereby, the fluid in the shell 50 passes, in sequence, through the fluid suction channel 65 of the back cover 66, the muffler 84, and the fluid suction channel 67 and the suction port 68 of the piston 69, to be suctioned into the compression chamber C. After being compressed by the piston 69 in the compression chamber C, the compressed fluid passes, in sequence, through the discharge valve assembly 70 and the discharge pipe 54 so as to be discharged to the outside.

Meanwhile, when the piston 69 rectilinearly reciprocates as stated above, and the fluid in the shell 50 is suctioned, compressed and discharged, the oil O received in the bottom region of the shell 50 is suctioned on the basis of pressure variation inside the oil pump 90. The suctioned oil O is used to lubricate/cool the cylinder 62 and the piston 69, and is discharged to the outside of the linear compressing unit 60.

Now, the pressure variation inside the oil pump 90 and the resulting oil supply procedure will be explained in more detail.

When the oil piston 94 moves backward, the oil suction valve 105 is opened to produce a low pressure in front of the oil piston 94. Thereby, the oil O, filled in the oil cylinder 93, is introduced to the front of the oil piston 94 via the oil channel 104 defined throughout the oil piston 94.

Here, the oil O, received in the bottom region of the shell 50 is introduced and filled in the oil cylinder 93 via the oil inlet 91 of the oil cylinder 93 not covered by the oil suction cover 103.

In succession, when the oil piston 94 moves forward, the oil suction valve 105 is closed to produce a high pressure in front of the oil piston 94, causing the oil discharge valve 106 to be opened. Thereby, the oil O, filled in the oil cylinder 93, passes, in sequence, through the oil passage 100, the cylinder frame suction channel 101 and the cylinder suction channel 102, to be supplied into the gap between the cylinder 62 and the piston 69, thereby serving to lubricate/cool the cylinder 62 and the piston 69.

Meanwhile, considering the assembling procedure of the linear compressing unit 60, the linear motor 61 is first located between the cylinder frame 63 and the stator cover 64, and the cylinder frame 63 and the stator cover 64 are axially fastened relative to each other by means of the bolts 107 and the nuts 108, so as to fix the outer stators 78 therebetween.

Here, since the stator cover 64 has the non-circular form having two or more curvatures, there is achieved an advantage in that a distance D′ between the stator cover 64 and the shell 50 increases as compared to a distance D defined when the stator cover 64 has a circular form. This enables reduction of the size of the shell 50, resulting in a small-scale linear compressor.

FIG. 6 is a front sectional view illustrating a linear compressor in accordance with a second embodiment of the present invention.

As shown in FIG. 6, the linear compressor according to the present embodiment comprises: a shell 120 for receiving oil O; a linear motor 121 mounted in the shell 120; a cylinder frame 122 mounted in front of the linear motor 121; a stator cover 123 mounted in rear of the linear motor 121; a piston 125 rectilinearly reciprocably disposed in a cylinder 124 mounted in the cylinder frame 122; fastening device for fixing the cylinder frame 122 and the stator cover 123 to each other; and oil supply device for supplying the oil O received in the shell 120 into a gap between the cylinder 124 and the piston 125.

The linear motor 121 comprises: outer stators 126 interposed between the cylinder frame 122 and the stator cover 123; a bobbin 127 provided inside the outer stators 126; a coil 128 wound on the bobbin 127; an inner stator 129 mounted on the cylinder frame 122 to be spaced apart from the outer stators 126 by a predetermined distance; a magnet 130 interposed between the outer stators 126 and the inner stator 129 to rectilinearly reciprocate by making use of electromagnetic force produced by the coil 128; and a magnet frame 131 coupled to a rear end of the piston 125 to fix the magnet 130 so that it transmits the rectilinear reciprocating movement of the magnet 130 to the piston 125.

The fastening device includes: bolts 132 having a predetermined length sufficient to axially penetrate through the cylinder frame 122 and the stator cover 123; and nuts 133 fastened to the bolts 132, respectively.

The oil supply device comprises: an oil pump 140 mounted between the cylinder frame 122 and the stator cover 123 to pump the oil O received in the shell 120; an oil suction channel 147 for introducing the oil O from the oil pump 140 into the gap between the cylinder 124 and the piston 125; and an oil discharge channel 148 for discharging the oil O between the cylinder 124 and the piston 125 to the outside of the cylinder 124.

The oil pump 140 has: an oil cylinder 143 having an oil inlet 141 and an oil outlet 142 formed at opposite ends thereof; an oil piston 144 rectilinearly reciprocably disposed in the oil cylinder 143; and first and second oil springs 145 and 146 disposed in the oil cylinder 143 to elastically support opposite ends of the oil piston 144.

The oil suction channel 147 is a combination of an oil passage 150, a cylinder frame suction channel 151, and a cylinder suction channel 152. The oil passage 150 is defined between the cylinder frame 123 and an oil discharge cover 149 mounted to the cylinder frame 123. The cylinder frame suction channel 151 is defined in the cylinder frame 122 to allow the oil suctioned through the oil passage 150 to pass through the cylinder frame 122. The cylinder suction channel 152 is defined to supply the oil suctioned through the cylinder frame suction channel 151 into the gap between the cylinder 124 and the piston 125.

The cylinder frame 122 is circumferentially formed with a plurality of through-holes 153 for the penetration of the bolts 132, and correspondingly, the stator cover 123 is circumferentially formed with a plurality of through-holes 154 for the bolts 132. The bolts 132, fastened through the through-holes 153 and 154, are finally fastened with the nuts 133.

FIG. 7 is a schematic side sectional view of the linear compressor shown in FIG. 6, illustrating how the stator cover 123 of the linear compressor is mounted.

As shown in FIG. 7, in the second embodiment of the present invention, the stator cover 123 has a non-circular form having two or more curvatures so that a section of the stator cover 123 not formed with the through-holes 154 has a curvature K 2 smaller than a curvature K 1 of the remaining section of the stator cover 123 formed with the through-holes 154.

In the present embodiment, one end of the oil cylinder 143, formed with the oil outlet 142, is supported against the cylinder frame 122, and the other end of the oil cylinder 143, formed with the oil inlet 141, is supported against the stator cover 123. In this case, it is preferable that a lower section of the stator cover 123 adapted to support the oil cylinder 143 has a curvature K 3 larger than the curvature K 2 of the upper section of the stator cover 123 not formed with the through-holes 154.

Here, the curvatures K 1, K 2 and K 3 are reciprocal values of radii of curvature ρ1, ρ2 and ρ3. The smaller the curvatures K 1, K 2 and K 3 are, the larger the radii of curvature ρ1 and ρ2, resulting in a smooth contour of the stator cover 123.

That is, the stator cover 123 is configured in such a fashion that the radius of curvature ρ2 of the section thereof not formed with the through-holes 154 is larger than the radius of curvature ρ1 of the section formed with the through-holes 154. With such a configuration, the stator cover 123 is spaced apart from the shell 120 by an increased distance, and the radius of curvature ρ3 of the lower section supporting the oil cylinder 143 is smaller than the radius of curvature ρ2 of the upper section of the stator cover 123 not formed with the through-holes 154. This enables the stator cover 123 to completely support the oil cylinder 143.

The stator cover 123 has an oil inlet 155 formed at a position corresponding to the oil inlet 141 of the oil cylinder 143 for allowing the oil O received in the bottom region of the shell 120 to be introduced via the stator cover 123.

The oil O received in the bottom region of the shell 120 passes, in sequence, through the oil inlets 155 and 141, and is filled in the oil cylinder 143. Then, on the basis of the rectilinear reciprocation of the oil piston 144, the oil is supplied into the gap between the piston 125 and the cylinder 124, serving to lubricate/cool the piston 125 and the cylinder 124.

Here, the stator cover 123 is easy to manufacture since it is fabricated through sheet metal forming.

As stated above, in the second embodiment of the present invention, the end of the oil cylinder 143 is directly supported by the stator cover 123 without requiring the oil suction cover, enabling a reduction in the number of elements and manufacturing cost thereof.

As apparent from the above description, the present invention provides a linear compressor having a stator cover, which is configured in such a fashion that a section not formed with bolt fastening through-holes has a curvature smaller than that of a section formed with the through-holes so as to enable a size reduction of the stator cover while defining a sufficient space between the stator cover and the shell. This enables reduction of the size of the shell, achieving a small-scale linear compressor.

Further, according to the present invention, a curvature in a lower region of the stator cover is larger than that of an upper region of the stator cover in order to sufficiently support an end of the oil cylinder without requiring a separate supporting element, such as an oil suction cover. Thereby, the number of elements constituting the linear compressor is reduced, resulting in a reduction of the manufacturing cost. By omitting the oil suction cover, further, it is possible to prevent a deterioration of oil supply efficiency caused when the oil suction cover is misassembled, thereby being capable of improving operational reliability and reducing noise produced due to shaking of the oil suction cover.

Although the preferred embodiment of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

1. A linear compressor comprising: a shell; a linear motor mounted in the shell; a cylinder frame mounted in front of the linear motor; a stator cover mounted in rear of the linear motor; a piston rectilinearly reciprocably disposed in a cylinder mounted in the cylinder frame; and fastening device for fixing the cylinder frame and the stator cover relative to each other, wherein the stator cover is formed to have two or more curvatures.
 2. The compressor as set forth in claim 1, wherein the stator cover has a plurality of through-holes for the penetration of the fastening device.
 3. The compressor as set forth in claim 2, wherein the stator cover is configured so that a curvature of a section of the stator cover not formed with the through-holes is smaller than a curvature of the remaining section of the stator cover formed with the through-holes.
 4. The compressor as set forth in claim 3, wherein the fastening device includes: bolts for axially penetrating through the cylinder frame and the stator cover; and nuts to be fastened to the bolts, respectively.
 5. A linear compressor comprising: a shell in which oil is received; a linear motor mounted in the shell; a cylinder frame mounted in front of the linear motor; a stator cover mounted in rear of the linear motor; a piston rectilinearly reciprocably disposed in a cylinder mounted in the cylinder frame; and oil supply device supported at opposite ends thereof against the cylinder frame and the stator cover and adapted to supply the oil received in the shell into a gap between the piston and the cylinder, wherein the stator cover is configured so that a lower section of the stator cover supporting the oil supply device has a curvature smaller than a curvature of an upper section of the stator cover.
 6. The compressor as set forth in claim 5, wherein the oil supply device includes an oil pump adapted to pump the oil received in the shell into a gap between the piston and the cylinder.
 7. The compressor as set forth in claim 6, wherein the oil supply device includes: the oil pump mounted between the cylinder frame and the stator cover to pump the oil received in the shell; an oil suction channel for introducing the oil from the oil pump into the gap between the cylinder and the piston; and an oil discharge channel for discharging the oil between the cylinder and the piston to the outside of the cylinder.
 8. The compressor as set forth in claim 7, wherein the oil pump has: oil cylinder having an oil inlet and an oil outlet formed at opposite ends thereof; an oil piston rectilinearly reciprocably disposed in the oil cylinder; and first and second oil springs disposed in the oil cylinder to elastically support opposite ends of the oil piston.
 9. The compressor as set forth in claim 8, wherein one end of the oil cylinder is supported against the cylinder frame, and the other end of the oil cylinder is supported against the stator cover.
 10. The compressor as set forth in claim 9, wherein the stator cover has an oil inlet formed at a lower region thereof to correspond to the oil inlet of the oil cylinder.
 11. A linear compressor comprising: a shell in which oil is received; a linear motor mounted in the shell; a cylinder frame mounted in front of the linear motor; a stator cover mounted in rear of the linear motor; a piston rectilinearly reciprocably disposed in a cylinder mounted in the cylinder frame; fastening device for fixing the cylinder frame and the stator cover relative to each other; and oil supply device for supplying the oil received in the shell into a gap between the piston and the cylinder, wherein the stator cover is formed to have two or more curvatures.
 12. The compressor as set forth in claim 11, wherein the stator cover has a plurality of through-holes for the penetration of the fastening device.
 13. The compressor as set forth in claim 12, wherein the stator cover is configured so that a curvature of a section of the stator cover not formed with the through-holes is smaller than a curvature of the remaining section of the stator cover formed with the through-holes.
 14. The compressor as set forth in claim 13, wherein the fastening device includes: bolts for axially penetrating through the cylinder frame and the stator cover; and nuts to be fastened to the bolts, respectively.
 15. The compressor as set forth in claim 14, wherein the oil supply device includes an oil pump adapted to pump the oil received in the shell into a gap between the piston and the cylinder.
 16. The compressor as set forth in claim 14, wherein the oil supply device includes: the oil pump mounted between the cylinder frame and the stator cover to pump the oil received in the shell; an oil suction channel for introducing the oil from the oil pump into the gap between the cylinder and the piston; and an oil discharge channel for discharging the oil between the cylinder and the piston to the outside of the cylinder.
 17. The compressor as set forth in claim 16, wherein the oil pump has: oil cylinder having an oil inlet and an oil outlet formed at opposite ends thereof; an oil piston rectilinearly reciprocably disposed in the oil cylinder; and first and second oil springs disposed in the oil cylinder to elastically support opposite ends of the oil piston.
 18. The compressor as set forth in claim 17, wherein one end of the oil cylinder is supported against the cylinder frame, and the other end of the oil cylinder is supported against the stator cover.
 19. The compressor as set forth in claim 18, wherein the stator cover is configured so that a lower section of the stator cover supporting the oil supply device has a curvature smaller than a curvature of an upper section of the stator cover.
 20. The compressor as set forth in claim 19, wherein the stator cover has an oil inlet formed at a lower region thereof to correspond to the oil inlet of the oil cylinder. 